This invention relates to an apparatus for capturing residual gas vapors that are under pressure in a tank. In particular, it relates to an apparatus that attaches to a tank that contains a gas under pressure, so that when the gas is released into the apparatus the gas is absorbed by a filter.
Every day in the United States millions of tons of hazardous liquid or liquefied chemicals are transported in tanks on trucks, trains, ships, and airplanes. While the tanks can usually be loaded safely, the removal of chemicals from the tanks at the customer""s site can be hazardous.
The chemicals can be removed from the tank by pumping them out or by forcing them out using air or nitrogen pressure. While pumping is relatively safe, the pressurization method, which is much more common, can be extremely dangerous and requires constant monitoring. The tank operator positions the bulk tank trailer in the proper unloading area, prepares the proper equipment for the delivery site, and dresses in his personal protection equipment. This equipment typically consists of rubber chemical boots, full body rubber suit, helmet with face shield, safety glasses, and a poisonous gas mask. After the operator gets dressed, he connects a hose of the proper size between the tank and the customer""s chemical inlet connection. He connects an air hose from an air compressor to the air inlet assembly on the tank, opens the air inlet valve, turns on the air compressor, and pressurizes the tank to between 20 and 28 psi. It is extremely important that the air pressure does not exceed the maximum allowable pressure psi or the safety caps will explode from the tank. If this happens, the pressurized gas will eject the chemical in the tank into the atmosphere at a high velocity. When the tank has been pressurized, the operator positions himself near the unloading valves. The customer""s chemical inlet valve is opened first, then the internal and external valves on the tank are opened and the chemical is forced into the customer""s chemical storage tank. When the operator""s tank is empty, the customer signs the proper paperwork and leaves. The driver closes all the valves and begins his clean up.
Unfortunately, there are still residual chemical vapors in the tank, typically under a pressure of about 15 to about 25 psi, which greatly exceed the pressure in the tank when it was loaded. Trucking companies typically have a policy that a truck cannot be driven with the tank under this much pressure. But under EPA regulations it is illegal for the operator to release these chemical vapors into the atmosphere. Faced with this dilemma, the operator almost always chooses to open the air inlet valve and release the vapors to the atmosphere. As he does this, he moves rapidly upwind to escape the hazardous gas cloud. Since customers"" sites are frequently near residential areas, people in the area are exposed to these vapors and may suffer various ailments, some serious or even deadly, without ever knowing the cause.
I have invented an apparatus for capturing the residual gases in a pressurized tank. The apparatus of this invention prevents the release of a residual gas to the environment after a tank containing the liquified chemical and has been emptied.
The apparatus is inexpensive and can be made disposable, reusable, and recyclable. It is attached to a tank after the tank has been emptied. The operator can then drive away from the site while the residual gas gradually leaves the tank and is captured by the filter.